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Publication numberUS4663130 A
Publication typeGrant
Application numberUS 06/551,116
Publication dateMay 5, 1987
Filing dateNov 14, 1983
Priority dateNov 14, 1983
Fee statusPaid
Also published asCA1230975A, CA1230975A1, DE3441582A1, DE3441582C2
Publication number06551116, 551116, US 4663130 A, US 4663130A, US-A-4663130, US4663130 A, US4663130A
InventorsRoger M. Bergman, Edwin J. Bielecki, Brian J. Higgins, Karl A. Romberger
Original AssigneeCabot Corporation
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process for dissolving tantalum/columbium materials containing alkali metal impurities
US 4663130 A
Abstract
Disclosed is a process for dissolving tantalum and/or columbium-containing materials contaminated with alkali metal impurities. The tantalum and columbium materials are digested in a solution comprising hydrofluoric acid and a fluosilicate-containing compound. The alkali metals are reacted to form precipitated fluosilicates, which then can readily be separated.
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Claims(18)
The embodiments of the invention in which exclusive property or privilege is claimed are defined as follows:
1. A digestion process for the recovery of tantalum and/or columbium values, wherein the improvement comprises: dissolving tantalum and/or columbium-containing materials, contaminated with alkali metal impurities, in a hydrofluoric acid solution containing a fluorosilicate compound in an amount sufficient to react with said alkali metal impurities to precipitate alkali metal fluosilicates.
2. The process of claim 1 wherein the fluosilicate compound is used in an amount of at least about one equivalent of fluosilicate per equivalent of alkali metal impurity.
3. The process of claim 1 wherein the fluosilicate compound is fluosilicic acid.
4. The process of claim 1 wherein the fluosilicate compound is ammonium fluosilicate.
5. The process of claim 1 wherein the fluosilicate compound is magnesium fluosilicate.
6. The process of claim 1 wherein the tantalum-containing material is tantalum-containing waste from the sodium reduction of potassium fluotantalate.
7. The process of claim 1 wherein the tantalum-containing material is potassium fluotantalate.
8. The process of claim 1 wherein the fluosilicate compound is generated in-situ in the hydrofluoric acid solution by the addition of a silicon-containing material to said solution.
9. The process of claim 1 wherein the tantalum and/or columbium-containing materials are dissolved in a hydrofluoric acid solution at a temperature ranging from about 70 to about 95 C. (343 to about 368 K.).
10. A process for dissolving tantalum and/or columbium-containing materials contaminated with alkali metal impurities comprising: dissolving the tantalum and/or columbium-containing materials in a hydrofluoric acid solution containing a fluosilicate compound in an amount sufficient to react with the alkali metal impurities to precipitate alkali metal fluosilicates.
11. The process of claim 10 wherein the fluosilicate compound is used in an amount of at least about one equivalent of fluosilicate per equivalent of alkali metal contaminant.
12. The process of claim 10 wherein the fluosilicate compound is fluosilicic acid.
13. The process of claim 10 wherein the fluosilicate compound is ammonium fluosilicate.
14. The process of claim 10 wherein the fluosilicate compound is magnesium fluosilicate.
15. The process of claim 10 wherein the tantalum-containing material is tantalum-containing waste from the sodium reduction of potassium fluotantalate.
16. The process of claim 10 wherein the tantalum-containing material is potassium fluotantalate.
17. The process of claim 10 wherein the fluosilicate compound is generated in-situ in the hydrofluoric acid solution by the addition of a silicon-containing material to said solution.
18. The process of claim 10 wherein the tantalum and/or columbium-containing materials are dissolved in a hydrofluoric acid solution at a temperature ranging from about 70 to about 95 C. (343 to about 368 K.).
Description

Tantalum and columbium-containing materials such as ores, scrap materials, and the like, commonly are processed by digesting the materials in hydrofluoric acid to thereby form soluble tantalum and columbium fluorides. The tantalum and columbium are separated from each other and purified from associated metallic contaminants through liquid/liquid extraction techniques, using any suitable, water-immiscible, organic solvent, commonly methyl isobutyl ketone (MiBK).

The hydrofluoric acid solution is contacted with the ketone, and, by utilizing the principle that tantalum will extract from an aqueous hydrofluoric acid solution into the organic phase at a lower acidity than will the columbium, the tantalum and columbium are separated.

In commercial operations, it is economically desireable to maintain high concentrations of tantalum and/or columbium in the hydrofluoric acid solution in order to allow high production rates from the plant, as well as to lower the variable manufacturing costs (e.g., use less hydrofluoric acid and MiBK per pound of tantalum or columbium produced). For economical operation, tantalum oxide (Ta2 O5) and/or columbium oxide (Cb2 O5) concentrations in the digest solution are typically in the range of about 40 to about 100 g/L (kg/m3) Ta2 O5 and Cb2 O5.

The tantalum and columbium-containing materials to be dissolved in hydrofluoric acid sometimes contain alkali metal contaminants, such as sodium and/or potassium. Such tantalum and columbium-containing materials typically may include, for example, such materials as recycled waste products from the sodium reduction of potassium fluotantalate, impure potassium fluotantalate, and various other Ta/Cb-containing materials with alkali metal impurities. When these contaminated materials are dissolved in hydrofluoric acid, the concentrations of the tantalum and columbium are limited by the presence of the alkali metals. For example, the low solubilities of such alkali metal compounds as sodium or potassium fluotantalates or many fluocolumbates cause these compounds to be lost due to precipitation.

Now, according to the present invention, it has been discovered that tantalum and/or columbium-containing materials contaminated with alkali metal impurities can be dissolved by a process comprising digesting the tantalum and/or columbium-containing materials in a hydrofluoric acid solution including a fluosilicate (SiF6 -2 -containing) compound to dissolve the tantalum and/or columbium and precipitate alkali metal fluosilicates. The precipitated alkali metal fluosilicates then can be separated from the dissolved tantalum and/or columbium.

Temperatures from ambient (about 25 C., 298 K.) up to the boiling point of the solution (about 100 C., 373 K., at standard pressure) typically are utilized; raising the temperature serves to increase solubilities and reaction rates. Preferably, the digestion is conducted at about 70 to 95 (343 to about 368 K.).

The fluosilicate may be introduced as any soluble fluosilicate compound during the initial ore digestion or any subsequent step in the process in which tantalum and/or columbium-containing materials are contacted with a hydrofluoric acid solution. Suitable compounds include fluosilicic acid (H2 SiF6), ammonium fluosilicate [(NH4)2 SiF6 ], magnesium fluosilicate (MgSiF6), and the like. The fluosilicate also may be introduced by production in situ, i.e. by reaction of hydrofluoric acid with a silicon-containing material, such as quartz or any silicate mineral. Using quartz addition as an example, in situ formation of fluosilicic acid is illustrated by the following equation: SiO2 +6HF→H2 SiF6 +2H2 O. Fluosilicic acid is preferred as the fluosilicate compound.

For purposes of illustration, using fluosilicic acid (H2 SiF6) as the soluble fluosilicate compound and potassium fluotantalate (K2 TaF7) as a tantalum-containing material, K2 TaF7 reacts to produce soluble fluotantalic acid (H2 TaF7) and precipitated potassium silicofluoride (K2 SiF6), according to the mechanism outlined in the equations below: ##STR1##

The precipitated potassium silicofluoride (K2 SiF6) readily can be separated by conventional techniques, such as filtration. With or without preliminary filtration, the tantalum-containing solution may then be contacted with a suitable organic solvent whereby tantalum and columbium values are selectively extracted using conventional liquid/liquid extraction techniques.

The fluosilicate compound should be used in an amount sufficient to reach with all of the alkali metal contaminant present to precipitate alkali metal fluosilicates. Accordingly, at least about one equivalent of fluosilicate should be used per equivalent of alkali metal.

Any suitable, water-immiscible, organic solvent may be used to extract the tantalum and columbium values. Typical solvents include ketones, alcohols, ethers, aldehydes, and the like. Ketones, such as methyl isobutyl ketone, diethyl ketone, and the like are preferred; methyl isobutyl ketone is particularly preferred.

The following examples are provided to further illustrate the invention. The examples are intended to be illustrative in nature and are not to be construed as limiting the scope of the invention. All percentages given are by weight, unless otherwise indicated.

EXAMPLE I

A two liter (0.002 m3) teflon beaker was fitted with an agitator comprising a polypropylene shaft and impellor connected to an electric motor, a teflon-covered copper heat exchanger coil, and a teflon-covered thermometer. To the beaker was added 0.4548 kg of deionized water (DI H2 O), 0.3743 kg of 49% by wt aqueous hydrofluoric acid (HF), and 0.335 kg of an aqueous 30% by wt fluosilicic acid solution (H2 SiF6). While stirring the mixture, water was circulated through the heat exchanger coil to cool the mixture to below 30 C., and then 0.300 kg of tantalum (Ta)-containing waste from the sodium reduction of K2 TaF7 (65.25% Ta, 4.5% Na, 7.9% K) was added slowly to the beaker over a period of about one hour (3600 seconds). The addition rate of the Ta-containing waste material was governed by the ability to maintain the temperature at less than 30 C. (303 K.) and to minimize foaming. After all of the tantalum material was added, the cooling water was disconnected and steam was introduced to the heat exchanger coil in order to heat the stirred mixture to 95 C. (368 K.) for about two hours (7200 seconds). Upon completion of reaction, the resulting slurry was cooled to less than 20 C. (293 K.) and then was filtered through a 10 micrometer membrane filter. The residue was washed by drawing a small quantity of 5% by wt aqueous HF solution through the filter cake; this was combined with the initial filtrate solution. The liquid volume and the tantalum content of the filtrate was measured; the amount of tantalum in the liquid phase then was calculated. The wet filter cake was dried at 120 C. (393 K.), the dry weight was measured, and the solids are analyzed for tantalum content. The percent of tantalum solubilization was calculated using the formula: ##EQU1## The results are reported in Table A, below:

COMPARATIVE EXAMPLE II

A second run was made using the same equipment, Ta input material, and general procedure as outlined in Example I above. In this example, however, no fluosilicate was included in the digestion mixture.

The results are reported in Table A, below:

              TABLE A______________________________________                    Comparative          Example I Example II______________________________________Digestion Mixture49% HF (kg)      .3743       .374330% H2 SiF6 (kg)            .335        0DI H2 O (kg)            .4548       .6897Ta-containing Material (kg)            .300        .300Ta Content (wt %)            65.25       65.25Digestion Liquor Volume (m3)            .900  10-3                        .880  10-3Ta content (g/L) (kg/m3)            209         109Digestion Residue (kg)            .1341       .2074Ta content (wt %)            9.1         45.6Ta Solubilized (wt %)            94          52______________________________________

As noted by a review of the table above, the digestion of the Ta-containing waste material in a hydrofluoric acid solution including fluosilicic acid accomplished solubilization of 94 percent of the tantalum content of the input material. Without the presence of fluosilicate in the digestion solution only 52 percent of the tantalum was solubilized.

EXAMPLE III AND COMPARATIVE EXAMPLE IV

Another set of runs were conducted using the same equipment and general procedures as outlined in Example I and Comparative Example II, above. Another typical Ta-containing waste sample from the sodium reduction of K2 TaF7 (68.82% Ta, 1.77% Na, 5.3% K) was used as the tantalum-containing material input. In Example III, fluosilicic acid was added to the digestion mixture, while Comparative Example IV included no fluosilicate in the digestion mixture.

The results are listed below in Table B. It can be noted that the digestion of Example III, including fluosilicic acid in the digestion solution, achieved 99 percent solubilization of the tantalum present in the Ta-containing input material. This is compared with a 79 percent solubilization in a digestion without fluosilicate present, in comparative Example IV.

              TABLE B______________________________________                    Comparative          Example III                    Example IV______________________________________Digestion Mixture49% HF (kg)      .3743       .374330% H2 SiF6 (kg)            .335        0DI H2 O (kg)            .454        .6897Ta-containing Material (kg)            .300        .300Ta Content (wt %)            68.82       68.82Digestion Liquor Volume (m3)            .960  10-3                        1.115  10-3Ta content (g/L) (kg/m3)            222         152Digestion Residue (kg)            .0753       .1142Ta content (wt %)            3.7         39.05Ta Solubilized (wt %)            99          79______________________________________
EXAMPLE V AND COMPARATIVE EXAMPLE VI

Again using the same equipment and general procedure as outlined in Example I, a run was made using a potassium fluotantalate sample (K2 TaF7) as tantalum-containing material input. Fluosilicic acid was added to the digestion mixture. The results, featuring 99 percent of the input Ta solubized, are reported in Table C, below. By comparison, if no fluosilicate is added to the digestion mixture, as shown in comparative Example V, the weight percent of tantalum solubilized is only about 7 percent.

              TABLE C______________________________________                    Comparative          Example V Example VI______________________________________Digestion Mixture49% HF (kg)      .0387       .038730% H2 SiF6 (kg)            .1286       0DI H2 O (kg)            .190        .315Ta-containing material (kg)            .100        .100Ta Content (wt %)            46.7        46.7Digestion Liquor Volume (m3)            .355  10-3                        .355  10-3Ta content (g/L) (kg/m3)            134.1       9Digestion Residue (kg)            .0542       .0929Ta content (wt %)            0.5         46.7Ta Solubilized (wt %)            99          7______________________________________

Similar digestion runs using various sources of fluosilicate exhibit comparable results to those reported above wherein fluosilicic acid was included in the digestion mixture. These other sources of fluosilicate include the in-situ generation of (SiF6 -2) by the addition of quartz or a silicate material to the digestion solution, as well as the addition of ammonium fluosilicate and/or magnesium fluosilicate. The above examples have reported tantalum solubilization; columbium-containing input materials dissolved in similar digestion mixtures produce comparable increases in solubilization of Cb by including fluosilicate in the digestion mixture, according to the present invention.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2816815 *Feb 16, 1955Dec 17, 1957Mallinckrodt Chemical WorksProcess for separating values of titanium from columbium and tantalum values
US3658511 *Dec 22, 1969Apr 25, 1972Kawecki Berylco IndUpgrading the tantalum and columbium contents of oxidic metallurgical products
US3972710 *Jul 9, 1975Aug 3, 1976Hermann C. Starchk BerlinMethod of upgrading tantalum and niobium concentration in slags
US4309389 *Jul 1, 1980Jan 5, 1982Hermann C. Starck BerlinProcess for the recovery of hydrofluoric acid and depositable residues during treatment of niobium- and/or tantalum-containing raw materials
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5620936 *Dec 14, 1993Apr 15, 1997E. I. Dupont De Nemours And CompanyRecovery of spent catalyst
US5635146 *Nov 30, 1995Jun 3, 1997Osram Sylvania Inc.Method for the dissolution and purification of tantalum pentoxide
US5728639 *Apr 17, 1997Mar 17, 1998E. I. Du Pont De Nemours And CompanyRecovery of spent catalyst
US6010676 *Sep 12, 1997Jan 4, 2000Osram Sylvania Inc.Method for making a highly pure tantalum compound
US6238494Sep 29, 1999May 29, 2001Johnson Matthey Electronics Inc.Polycrystalline, metallic sputtering target
US6800259Mar 4, 2002Oct 5, 2004Cabot CorporationMethods to control H2S and arsine emissions
US6843970Mar 26, 1996Jan 18, 2005Cabot CorporationProcess for recovering metal values by dissolving them in a sulfuric acid solution containing a carbon source and a reducing agent
US6979429Nov 5, 2002Dec 27, 2005Cabot CorporationMethod for solubilizing metal values
US7282187Mar 26, 1996Oct 16, 2007Caboi CorporationRecovery of metal values
US20030165416 *Mar 4, 2002Sep 4, 2003Hard Robert A.Methods to control H2S and arsine emissions
US20030170158 *Nov 5, 2002Sep 11, 2003Hard Robert A.Method for solubilizing metal values
EP1633896A1 *Dec 19, 2003Mar 15, 2006Advortech Holdings Pty Ltd.Process for purifying inorganic materials
WO1990002823A1 *Aug 4, 1989Mar 22, 1990Institut National De Recherche Chimique AppliqueeIMPROVED PROCESS FOR OBTAINING IMPURITY-FREE COMPOUNDS OF Ta AND/OR Nb FROM MATERIALS CONTAINING THESE METALS
Classifications
U.S. Classification423/68, 423/63
International ClassificationC01G35/02, C22B34/24, C01G35/00, C01G33/00
Cooperative ClassificationC22B34/24, C01G35/003, C01G35/02, C01G33/00, C01G33/003
European ClassificationC01G33/00, C22B34/24, C01G35/02, C01G35/00B, C01G33/00B
Legal Events
DateCodeEventDescription
Nov 14, 1983ASAssignment
Owner name: CABOT CORPORATION 125 HIGH STREET, BOSTON MA 0211
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:BERGMAN, ROGER M.;BIELECKI, EDWIN J.;HIGGINS, BRIAN J.;AND OTHERS;REEL/FRAME:004197/0177
Effective date: 19831031
Oct 22, 1990FPAYFee payment
Year of fee payment: 4
Sep 26, 1994FPAYFee payment
Year of fee payment: 8
Oct 30, 1998FPAYFee payment
Year of fee payment: 12